Electric arc lamp



April 17, 1934.

B. OBRIEN ELECTRIC ARC LAMP Filed April 15, 1930 4 Sheets-Sheet 1 April17, 1,934. a. @BRIEN 1,955,143

ELECTRIC ARC LAMP Filed April l5, 1930 4 Sheets-Sheet 2 April 17, 1934.Bl QBRlEN 1,955,143

ELECTRIC ARC LAMP Filed April l5, 1930 4 Sheets-Sheet 3 S11/vento April17, 1934. B. O'BRIEN 1,955,143

ELECTRIC ARC LAMP Filed April 15, 1930 4 Sheets-Sheet 4 :Erika 0:371

Patented YApr. 17, 1934 UNITED STATES PATENT OFFICE 22 Claims.

This invention relates to electric arc lamps and more particularly toimprovements in mechanisms for automatically regulating the movement ofthe controlled electrode. A mechanism for this purpose must function;first, to permit the electrodes to'be moved together to start the arc,second, to separate the electrodes to produce the required length of arcand, third, to feed the controlled electrode at a speed determined bythe rate at which the electrodes are consumed, to maintain the requiredlength of the arc. l

One object of the invention is to provide a mechanism of the kindgenerally described which, upon establishmentof a circuit through theelectrodes, separates them to produce the required length of arc, feedsthe controlled electrode silently and evenly at a speed determined bythe consumption of the electrodes to maintain the required length of arcand which when the arc is extinguished for any reason, for example, asby being blown out or by suspension of current supply, is operative tobring the electrodes together so that the arc circuit may bere-established, whereupon the cycle of operations described-is repeated.

Further objects are: a mechanism in which one of the electrodes may beuniversally adjusted thereby facilitating their alignment even thoughone/or both of them may be warped; a mechanism -in which the electrodesare held by their extremities, hence permitting their completeconsumption without adjustment of their holding means; a mechanism inwhich the clutch does not engage the controlled electrode, this objectcontemplating the use of a holder and having the advantage that theaction of the regulating mechanism is not affected by the physicalcharacteristics of the particular electrode in use;' a mechanism whichmay be set to stop automatically the feeding movement of the controlledelectrode after there has been a predetermined electrode consumption;and a mechanism in which the actuating means is damped at all times,thereby insuring a smooth feed of the controlled electrode.

The invention is illustrated in the accompanying drawings, in whichz YFigure 1 is a front elevation of an electricarc lamp constructed inaccordance with the invention.

Figure 2 is a longitudinal section-along line 2-2 of Figure 1.

Figure 3 is an enlarged section of the upper electrode holder takenalong line 3-3 of Figure 2.

Figure 4 is a transverse section of the same taken along line .4 4 ofFigure 2.

Figure 5 is a detail section of the holder for the upper electrode takenalong line 5--5 of Figure 2.

Figure 6 is an enlarged section of the lower 60 electrode holder takenalong line 6--6 of Figure 2.

Figure 'l is a detail section of the holder for the lower electrodetaken along line 7-7 of Figure 6.

Figure 8 is an enlarged detail section of the clutch mechanism takenalong line 8-8 of Fig- 65 ure 2, the clutch being shown in operativeposition.

Figure 9 is a section of the same taken along line 9-9 of Figure 8.

Figure 10 is an enlarged transverse section 70 taken along line 10-10 ofFigure 2.

Figure 11 is a section taken along line 11-11 of Figure 10.

Figure 12 is a detail'view showing thev lower electrode holder locked inits down position.

Figure 13 is a detail view of the lower electrode holder showing meansfor preventing its further movement after there has been'a predeterminedconsumption of the electrode.

Figure 14 is a fragmentary section taken along line 14-14 of Figure 1,showing a receptacle in one of the tubular supports for the discardedelectrodes.

Figure 15 is a fragmentary section taken along line 15-15 of Figure 1showing a receptacle in the other tubular support for containing thesupply of unused electrodes.

Figure 16 is a diagrammatic view showing the wiring system.

Figure 17 is a diagrammatic View showing pull curves for the solenoidand spring employed in the feed regulating mechanism.

Figure 18 is an enlarged section of the lower holder assembly showingthe mounting of the electrical conductor which leads to the lowerelectrode. g

In the illustrated/embodiment of the' invention, the mechanism forregulating the movement ofthe controlled electrode is shown inconnection with' a lamp suitable for therapeutic or other purposes. Itis to be understood, however, that the invention is concerned 'primarilywith the feed mechanism per se which, of course, is not dependent uponassociated mechanisms which may be utilized in adapting it to meet the.l requirements of different uses.

The lamp,as illustrated, is mounted upon a suitable base or pedestal 20and is supported thereon by a frame which includes a pair of maintubular supporting members 21 and a pair of auxiliary tubular Supportingmembers 22. A

-cross member 23 is suitably secured for adjustment upon the maintubular members 21, and.

provides a support for the auxiliary vtubular members 22. The members 22are mounted in suitable openings formed in the cross member 23 andextend below it to support a second cross member 24. The auxiliarytubular members 22 are preferably secured for adjustment to the crossmember 23 and carry at their upper ends a cross head 25, the latterbeing preferably hollow as best shown in Figure 2.

. The two electrodes 26a and 27a of the arc lamp are arranged forco-operation in the auxiliary -frame provided by the auxiliary tubularmembers. The upper electrode 26a is secured in a holder 26 which issupported by the cross head 25 for universal adjustment. For thispurpose, the holder 26 is formed with a flattened ballshaped head 28(Figs. 2, 3 and 4) which ts in a socket provided in the cross head. Thesocket consists of an opening 29 in the rear wall 30 of the crossmember,Y the said opening being of a smaller diameter than the ball 28,A second opening 31 is formed opposite the opening -29 in the front wallof the crosshead, the last mentioned opening having mounted therein acupshaped cap 32. The cap 32 may be adjusted with respect to the ball 28by means of a plate 33 which is secured at either side of the cap to thecross head. In securing the holder- 26 to the cross head 25 foruniversal adjustment, the plate 33 is loosened and the head 28 isinserted through an opening 34 in the lower wall of the cross head withits flattenedsides extending lengthwise of the head. vThe head is thenrotated through an angle of ninety degrees to thel position shown inFigure 4, whereupon the plate 33 may be tightened.

The holder 26 includes a body 35 (Figs. 3 and 5) to which the upperelectrode is' secured and which is insulated from the head 28 as by aninsul lating disc 36, the head and body portions of the holder beingprovided with cup shaped recesses within which the insulating disc fits,thereby preventing its disintegration even though it becomes cracked orotherwise injured in use. The head 28, body 35, and interposedinsulating disc 36 are secured together as a unit by a rod 37 which isconnected to the body 35 but insulated from the head 28 by the oversizeopening 38 through which it extends and by the insulating washer 36. Inthis connection, it will be understood, of

course, that the rod 37 also functions as a conductor to form part ofthe arc circuit. The electrode 26a is adapted to be removably secured tothe body 35. To this end the said body is formed with a V-shaped slot inwhich the terminal portion of the electrode may be positioned andsecured as by a plate 40 (Fig. 5). A baille plate 41 having a centralopening through which the electrode passes is secured in spaced relationwith respect to the body35, the said baille plate being designed toprevent overheatingI of the electrode holder. By Virtue of the universaladjustment of the upper holder 26, fresh electrodes may be readilyaligned at the outset of their use so that they will co-operate withoutfurther adjustment, until one of them is substantially entirelyconsumed` and this despite the fact that the electrodes, which aresupported by the extremities,

. may be warped.

t \As'illustrated, the lower electrode 27a is mountfed for axialmovement toward the upper electrode 26a, the fo'ij'men'for.conveniencebeing hereinafter designated as the controlled or lower electrode. 'I'hecontrolled electrode is carried'by a holder 27 which is substantiallysimilar to the upper holder 26 and is best shown in 'Figure 6. Itincludes a body 42 to which the lower electrode is clamped as by a plate43 (Fig. 7) A baffle plate 44 is secured to the upper face of the bodybut in spaced relation therewith, the said baille plate being designedto prevent overheating of the holder 27.

The lower holder also includes a hollow stem 45 which is insulated fromthe body 42 of the holder as by an insulating disc 46, the latter beingpositioned in cup shaped recesses formed in the lower face of the bodyand the upper end of a flanged member 47 which is secured to the stem45. A lower cross head 48 is included in the lower holder assembly andis formed with a pair of laterally extending arms 49. The various partsof the assembly are secured together as a unit by a longitudinallyextending rod 50 which is connected tc the body 42 of the holder but isinsulated from the stem 45. To this end, therefore, the said rodissmaller in diameter than the opening through the stem, this constructionproviding an insulating space between the rod and the stem. Aninsulating bushing 51 (Fig. 18) is mounted in the lower -end ofthestemto extend beyond said end so that the nut 52 upon the lower endof the rod may be tightened to draw the elements of the assemblytogether. In this connection, it is to be noted that during suchtightening the rod 50 is tensioned and hence avoids possibility of itscontacting withthe inner wall of the stem. However, if desired, aninsulated spacer 53 may be mountedupon the rod 50 to insure this.

The lower holder 27 is mounted for movement in the frame of the lamp bymeans of its stem 45. For this purpose, opposed bosses 54 which carryupper and lower bushings 55 and 56 respectively are formed in the crossmember 23. The bore of the upper bushing 55 is enlarged at its upper endto provide a chamber to receive a packing ring 57 which is held thereinin any suitable manner, the said ring being adapted to wipe the stem 45during movement of the holder.

Means is provided which normally tends to lift the lower holder 27toward the companion holder 26. This means includes a pair of weights 58which are connected to the laterally extending arms 49 of the lowercross head 48 as by strands 59 (Fig. 2). In order that the weights 58act in the manner described; the strands 59 pass over pulleys 60 whichare secured to the cross member 1 23. As stated, the weights 58 normallyurge the stem 45 and the holder 27 carried thereby toward the upperholder 26. In order to prevent sudden movements, either up or down, ofthe lower holder, means is provided for damping all y f may be filled byany suitable fluid 62 which is i utilized to prevent` sudden movement oftheweights 58 in either direction. The relative diameters of thereceptacles 61 and the enlarged `portions of the weights 58 may bevaried to meet.

different requirements.

The upward movement of the lower holder 27 I resulting from the actionof the weights 58 is, of course, faster than the rate of consumption ofthe electrodes. yIt is, therefore, necessary to provide means which willfunction to counteract the action of the weights 58, either. entirely orin part, so that the movement of the lower electrode 27a may becontrolled to establish and'maintain a substantially uniform arc. Tothis end, a clutch 63 is employed which is operative to engage andrelease the stem 45 as required. The said clutch is mounted upon thestem 45 within the cross member 23. It includes a pivoted member 64(Fig. 8) which is provided With a gripping ring 65, the latter having acentral opening relatively greater in diameter than the outer diameterof the stem 45, and being tapered from its upper edge toward the said.,stem. In this connection it is to be noted that the stem 45 is fitted inupper and lower'bushings 66 and 67 respectively, and that while thebushings 66 and 67 are concentric with the stem 45 the gripping ring ismounted in eccentric relation with respect to the said stem. Thegripping ring 65 is normally urged upwardly about its pivot by a spring68, which is compressed between the free end of the pivoted member 64and a shoulder 69 formed on thebody of the clutch, to engage the stem 45and urge it against the opposite side of the bushing 66. With thegripping ring functioning -in this manner, the clutch and stem 45 'aretightly secured against relative longitudinal movement. The clutch isreleased by the depression of the pivoted member 64 against the actionof its operating spring 68. This is accomplished by a pivoted operatingelementv 70 which is rforked at its free end to embrace the stem 45 'andextend beneath the bushing 55. The operating element 70 normally extendsangularly toward the bushing 55v with respect to the pivoted member 64of the clutch by virtue of a pin 71 carried by the said element andresting upon the pivoted member. From this it will be apparent that bydepressing the operating element 70 movement is transmitted through thepin 71 to the pivoted member 64 to move it downwardly against the actionof the spring 68. The downward movement of thesaid pivoted member, ofcourse, results in the gripping ring 65 moving toward a concentricposition with'respect to the stem 45 and results inthe release of thesame.v

The clutch`63 is connected by a pair of links 72 (Fig. 11) to ahorizontal member 73 which is pivotally mounted upon a transverse pin 74supported by upstanding lugs 75 preferaby formed integral with the crossmember 23. The pivotally mounted member 73 includes a pair of arms 76which are spaced to straddle the sleeve 77 of the clutch at a sufcientdistance therefrom so that they may overlie and be connected to thelower ends of the links 72. vAt one end, the arms 76`are connected to anarmature 80 which is mounted for movement in a solenoid 81. lThesolenoid is supported upon'a suitable base 82 which carries a pair ofopposed pulleys 83, the latter engaging the armature along its marginsto prevent vibration.

In this connection it isto be noted that the solenoid 81 is, as shown inFigure 16,l connected in series with the arc of the lamp, hence as theelectrodesy are consumed and the arc`becomes longer thetotal impedancein the arc circuit increases correspondingly. As the arc circuit isconnected to a source of supply of a constant potential, an increasein^the arc length results in a decrease in the current. Thus as the arcincreases or decreases in` length, the solenoid being in series with thesaid arc pulls more or less upon the armature with av corresponding pullupon the clutch 63. At" this pointit 'should be noted that each time theelectrodes are brought together to start the arc the clutch is adaptedto Withdraw the lower electrode to establish the required length of arc.In this movement, of course, the clutch is moved away from the bushing55 against which it abuts to effect its release from the stem of theholder. It is, therefore,

y necessary that the actuating or regulating mechanism be designed sothat the lower electrode will be fed at a rate determined by theconsumption of the electrodes until the operating member of the clutchhas engaged the bushing 55 to effect its release, from this point on thefeeding of the electrode. being effected by the slipping of the clutch.In other words, after the required arc has been established the clutchmoves through a determined range while it is engaging the stem of theelectrode before it permits slippage of the holder. 'Ihis being thecase, it is at once obvious that as the movement of the clutch whileit-is engaged with the stem 45 is regulated by the solenoid 81, that thearmature of the said solenoid must also have a range of vmovementdetermined by the range of movement of the clutch. As it is intendedthat an arc of a substantially uniform length be maintained at'alltimes, the current must remain constant. However, the current beingconstant, the pull upon the armature 80 varies depending upon theposition in its range of movement, as is graphicaly shown in Figure 17.In order to` counteract the action of the solenoid to such an extentthat the resultant force acting upon the pivoted member 73 issubstantially the. same anywhere within the' range of movement of theclutch 63 I employ a spring 79 in conjunction with the solenoid 81. Thisspring isIconnected to the opposite end of the pivoted member 73 whichis formed into a solid extension, lthe said extension projecting aroundand in front of a main tubular support 21 tol form a handle 78.

The range of movement of the armature 80 represents only a part of thetotal effective range of the solenoid. A graphic representation of the.pull of the spring 79 is shown in Figure 17 in connection with theillustration of the pull curve of the solenoid 81. It will be noted thatthat portion 83 ofthe solenoid pull curve which represents the pull ofthe solenoid in the range of movement utilized is substantially the sameas that portion 83a of the straight line representing the spring pull,it being understoodof course, that the-spring pull is opposite to thatof the solenoid pull. The weights 58, as stated, tend to lift the holder27 and this force is, of course, added to that of the spring 79. Thus itis evident that for a fixed value of current, the pull of the spring 79plus the unbalanced weight of the weights 58 is equal to tne pull of thesolenoid 81 at any point between a and b.

With this arrangement, assuming the arc has just been started, the lower4electrode is retracted to establish the required arc, in which movementthe clutch is withdrawn out of contact with the bushing 55. As theelectrodes are consumed with an increase in voltage and decrease incurrent, the solenoid is correspondingly affected, that is to say, itspull is weakened and it permits the spring 79 and weights 58 to feed theelectrode and keep the are uniform. In a like manner, when theelectrodes are initially brought together and there is a large amount ofcurrent flowing through them, the solenoid is effective, against thespring 79 and weights 58, to lengthen the arc.

In other words, this neutral equilibrium for a constant current becomesa stable equilibrium,

since the solenoid opens the arc to such a length.

that the current equals that for which the spring and solenoid pullcurves become equal. This enables the production of the required arc ata normal current value and insures its maintenance even after theelectrodes have been consumed to such an extent as to require clutchslipping.

In connecting the lamp to a source of supply, a Wire A (Fig. 16) leadingto one side of the power line is connected to the solenoid 81 and fromthe solenoid is connected to the end of the rod 50, there being a looselead or pigtail interposed between the latter two connections to permitmovement of the stem 45. The circuit continues from the rod 50 to thebody 42 of the lower holder 27. From the lower holder, that path ofcurrent is through the electrodes 27a and 26a to the upper holder 26.Two wires 84 and 85, in parallel, are connected to a wire B which leadsto the other side of the power line, one of these wires being returnedthrough each of the auxiliary tubular members 22. The current is dividedi'n this manner so that the arc will be equally repelled by both of themagnetic fields set up bythe current passing through the wires 84 and 85and hence remain straight, thus facilitating the uniform emission oflight in all directions. However, if it is desired that the light beemitted more in the direction of one of the tubes 22 .than the other allof the current may be passed through one of the wires depending upon thedirection in which the light is to be emitted.

In order to indicate whether the power is off or on when the electrodesare separated and no current is flowing, a pilot light 86 may beconnected across the two electrodes. The power being on and theelectrodes separated with no current flowing the light will glowbrightly.

- When the arc is established, the light will still be illuminated butless brightly since the voltage across the electrodes is lessened,whenthe arc is established, by the amount `of the voltage drop.

in the ballast resistance or inductance in the arc circuit. I

Suitable means is provided whereby the feeding movement of the ylowerelectrode 27a may be automatically stopped after there has been apredetermined consumption of the electrodes, said means, as illustrated,including an eye 87 and companionhook 88 which' are formed respectivelyupon the lower holder 27 and cross member 23. As best shown in Figure13, the

ysaid hook and eye are adapted to co-operate' with a chain 89 or othersuitable means whereby when there has been a predetermined upwardmovement of the holder 27 the chain will become eiective to prevent itsfurther movement.' By virtue of this arrangement, accidental operationof the'lamp beyond the time required is pre,- vented and allowance isthereby automatically made for intervals during which the lamp is not inoperation, that is to say, during such periods as the `arc may be blownout or the power shut 01T. When the lamp is not in operation the holder27, which will always move to the limit of its upward movement, may belheld` in its down position by a link 92.

The space within the main tubular supporting members 21 may befutilizedto storeused and fresh electrodes. For this purpose, receptacles 90and91, illustrated in Figures 14 and 15 respectively,'r`n`ay be removablysupported in the Aupperends of the said members, the receptacle 90 beingavailable yfor used or discarded elec- Lsama I trodes while thereceptacle l91 is available for containing a supply of fresh electrodes.

In the use of the lamp, the electrodes being connected to a source ofpower, the pilot light 86 glows brightly. Upon removal of the latchinglink 92, the holder 27 is released and with the clutch 63 is movedupwardly, the clutch releasing the stem 45 as it moves against thebushing 55 to permit continued upward movement of the holder until theelectrode '27a carried thereby touches the companion electrode 26a. Apath of current is thereupon established through the electrodes and thesolenoid 81. The solenoid acting upon the armature retracts the clutch63. During its initial downward movement, While it is engaging thebushing 55,

the clutch has no eiect upon the stem 45 ofthe holder. However, uponcontinued downward movement the clutch 63 first engages the stem 45 andupon further downward movement pulls with it the holder 27 to a distancedetermined by the required arc. When this arc has been established, thepivoted operating element 70 of the clutch is spaced from the bushing 55which effects the operation of the same as shown in Fig. 8. As theelectrodes are consumed, the solenoid 8l functions, in the mannerdescribed to move the clutch and hence the holder carried thereby tocompensate for such consumption. This feeding movement of the clutchcontinues until the pivoted operating element 70 engages the bushing 55whereupon continued movement of the clutch effects release of the stemthereby permitting the weights 58 to effect a further upward movement ofthe holder 27. The clutch permits this movement until the current in thecircuit has again reached the required value whereupon it again engagesthe stem 45. Thus, as the electrodes are consumed, th'e clutch permitsslippage of the holder 2 7 under the influence of the weights 58 at arate commensurate with Ktheir consumption.

It is to be noted that the inertia of the feed mechanism is large ascompared to the Weight which produces its motion. Further, by dampingthe feed mechanism instead of the solenoid or cross member which have amuch less effective inertia, the acceleration of the mechanism is smallwhen the clutch is released. This permits .a smooth feed as the progressof the mechanism is by small-increments.

Having fully described my invention I claim:

1. In an electrode feed mechanism, an electrode holder, means for movingsaid holder in the. direction of feed, means for engaging, said holderwithin a range of its movement, means for regulating the movement ofsaid holder within said range so as to maintain a substantially uniformarc, means operative upon said holder reaching the limit of said rangeto render said engaging means inoperative and thereby permit said holderto be moved further in the direction of feed and means for stopping thefeeding movement of the holder after a predetermined consumption of theelectrode carried'by it, said last named means being adjustable wherebythe amont'of such consumption may be varied at will.

.2. In an electrode feed mechanism, an electrode holder, means normallytending to move said holder in the direction of feed, means for engagingsaid holder within a range of its movement, means for regulating themovement of .said holder within said range so as to maintain asubstantially uniform arc, means operative upon said holder reaching thelimit of said range to render said engaging means inoperative andthereby permit said holder to be moved further in the direction of feedand means for stopping the feeding movement of the holder after apredetermined consumption of the electrode carried by it, said lastnamed means being adjustable whereby the amount of such consumption maybe varied at will.

3. In an electrode feed mechanism, an electrode holder, means normallytending to move said holder in the direction of feed, means for engagingsaid holder within a range of its movement, means for regulating themovement of said holder Within said range so as to maintain asubstantially uniform arc, said regulating means adapted to overcomesaid means normally tending to move the holder in the direction of feedshould the arc become too short, means operative upon said holderreaching the limit of said range to render said engaging meansinoperative and thereby permit saidholder to be moved further in thedirection of feed and means for stoppingthe feeding movement of theholder after a predetermined consumption of the eleotrode carried by it,said last named means being adjustable whereby the amount of suchconsumption may be varied at will.

4. In an electrode feed mechanism, an electrode holder, means for movingsaid holder in the direction of feed, means for engaging said holderwithin a range of its movement, means for regulating @the movement ofsaid holder within said range so as to maintain a substantially uniformare, means operative upon said holder reaching the limit of said rangeto render said engaging means inoperative and thereby permit saidholdfor stopping the feeding movement of said holderl after apredetermined consumption of the electrode carried by lt.

5. In an electrode feed mechanism, an elec-l trode holder, means forlifting said holder to feed the electrode carried thereby, means forengaging said holder within va range of Aits movement, means forregulating the movement of said holder within said range so as tomaintain a substantially uniform arc and means operative upon saidholder reaching the upper limit of said range to render said engagingmeans inoperative and thereby permit said electrode to be lifted furtherto compensate for its further consumption and thereby prevent increasein the arc length.

6. In an electrode feed mechanism, an electrode holder, means normallytending to lift said holder to feed the electrode carried thereby, meansfor engaging said holder within a range of its movement, means forregulating the movement of said holder within said range against the"action of said lifting means ,if the arc is too short so as to maintaina substantially uniform arc and means operative upon said holderreaching the upper limit 'of said range to render said engaging meansinopeative to thereby permit said lifting means to feed said electrodefurther and compensate for its further consumption.

7. In an electrode feed mechanism, an electrode holder, a weight forlifting said holder to feed the electrode carried thereby, `means' forengaging said holder within a range of its movement, means forregulating the movement of said holder within said range so as tomaintain a lsubstantially uniform arc and means operative upon saidholder reaching the upper limit of operative and thereby permit saidweight to lift said holder and feed said electrode.

8. In an electrode feed mechanism, an electrode holder, means for movingsaid holder in the direction of feed, a clutch engaging said holder in arange of its movement, said clutch including a pivoted gripping member,resilient means for forcing said gripping member into engagement withsaid holder and a pivotally mounted operating element for compressingsaid resilient means to release said gripping member, means forregulating the movement of said holder in said range to maintainsubstantially uniform arc and means operable upon said holder reachingthe limit of movement in said range for operating said operating element-to release said gripping member and permit said moving means to movesaid holder further in the direction of feed.

9. In an electric arc lamp, a movable electrode, a holder for saidelectrode, means for moving said holder to feed said electrode towardthe companion electrode, means for engaging said holder within a rangeof its movement, means tending to move said engaging means and theholder carried thereby toward the companion electrode, means responsiveto current changes in the are circuit .resulting from changes indistance between the electrodes as they are consumed for counteractingboth of said moving means more or less and thereby maintain asubstantially uniform arc and means for rendering said engaging meansinoperative upon said holder reaching the limit of its range of`movement and thereby permit said moving means first mentioned to movesaid holder further and feed said electrode.

10. In an electric arc lamp, a movable electrode, a holder for saidelectrode, means for moving said holder to feed said electrode towardthe companion electrode, means for engaging said holder within a rangeof its movementbresilient means tending to move said engaging means andthe engaged holder toward the companion electrode, means responsive tocurrent changes in the arc circuit resulting from changes in thedistance between the electrodes as they are consumed for counteractingboth of said moving means more or less and thereby maintain asubstantially uniform arc and means for rendering said engaging meansinoperative upon said holder reaching the limit of said range andthereby permit said means first mentioned to move said holder furtherand feed said electrode further.

l1. In lan electric are lamp, means for maintaining a substantiallyuniform arccomprising a movable electrode, an electrode holder, meansfor moving said holder to feed said electrode, means engaging saidholder Within a range of its movement, means for regulating the feed ofsaid electrode within said range, means operative upon said holderreaching the limitv of said range and there being a further consumptionof the electrode to render said engaging means inoperative and permitsaid electrode to be moved further by said first named means Ytomaintain a uniform arc,

said engaging means being again rendered operative upon further movementof the electrode to a suitable extent.

12. In an electric arc lamp, means for maintaining a substantiallyuniform arc comprising a. movable electrode, an electrode holder, vmeansnormally tending to move said holder to feed said electrode, meansengaging said holder within a range of itsmovement, means for regulatingthe feed of said electrode within said range, means operative upon saidholder reaching the limit of said range and there being a furtherconsumption of electrode to render said engaging means inoperative andpermit said electrode to be moved further by said rst named means so asto maintain a uniform are, said engaging means being again renderedoperative upon movement of said electrode to a suitable extent.

13. In an electric arc lamp, means for maintaining a uniform arccomprising a movable electrode, an electrode holder, means for movingsaid holder to feed said electrode, a clutch normally engaging saidholder within a range of its movement, means for regulating the feed ofsaid electrode within said range, means operative upon said holderreaching the limit of said range and there being further electrodeconsumption to release said clutch and permit further movement of theelectrode by said 'first named means thereby to maintain a uniform arc.

14. In an electric arc lamp, means for maintaining a substantiallyuniform arc comprising a movable electrode, an electrode holder, meansacting on said holder to feed said electrode, a clutch normally engagingsaid holder within a range of its movement, means acting on said clutchto move it in the direction of feed, means responsive to current changesin the arc circuit resulting from changes in distance between theelectrodes as they are consumed for counteracting in 'said range, saidmeans acting on said holder and said means acting on said clutch more orless and means for releasing said clutch when said holder reaches thelimit of said range and there being av further consumption of i theelectrode whereby said means acting on said holder moves it and saidelectrode further to a suitable extent.

15. In an electric are lamp, means for maintaining a substantiallyuniform arc comprising a movable electrode, an electrode holder, meansacting on said holder to feed said electrode, a clutch normally engagingsaid holder within a range of its movement',means acting on said clutchto move it in the direction of feed, means responsive to current changesin the arc circuit lresulting from changes in distance between theelectrodes as they are consumed for counteracting Within said range,said means acting on said holder and said means acting on said clutchand thereby maintain a substantially uniform arc and means for releasingsaid clutch when said holder reaches the limit of said range and therebeing a further consumption of the electrode whereby said means actingon said holder moves itand its electrode further to a suitable extent,said clutch being again rendered operative upon such occurrence.

16.In an electric arc lamp, means for maintaining a substantiallyuniform arc comprising a movable electrode, an electrode holder, meansacting on said holder to feed said electrode, a clutch normally engagingsaid holder within a range of its movement, resilient means acting onsaid clutch tending to move itin the direction of feed, means responsiveto changes in current in the arc circuit resulting from changes in thedistance between the electrodes as they are consumed for counteractingwithin said range, said means acting on said holder and said resilientmeans acting on said clutch, the said counteracting means being( adaptedto balance at any point in said range both said means acting to movesaid holder and said resilient means acting on said Clutch therebymaintaining a substantially constantl arc and means for releasing saidclutch when said holder reaches the limit of said range and there beinga further consumption of the electrode whereby said means acting on saidholder moves it further to feed said electrode to compensate for suchconsumption.

17. In an electric arc lamp, an electrode holder comprising a body towhich an electrode is secured, a hollow stem connected to but insulatedfrom' said body, an electrical conductor in said stem connected to saidbody but insulated from said stem, means for moving said holder andmeans engaging said stem for regulating the movement of said holder.

18. In an electric arc lamp,an electrode holder comprising a bodytowhich an electrode is secured, a hollow stem connected to butinsulated from said body, an/ electrical conductor held in said stemunder tension and connected tosaid body but insulated from said stem,means for moving said holder and means engaging said steml forregulating the movement of said holder. 19. In an electric arc lamp, anelectrode holder comprising a body to which an electrode is secured, ahollow stem connected to but insulated from said body, an electricalconductor in said stem connected to said body but insulated from sadstem, means for moving said holder in the direction of feed, meansengaging said stem within a range of movement of said holder, means forregulating the movement of said holder-Within said range so as tomaintain a substantially uniformare and means operative upon said holderreaching the limit of said range to render said engaging meansinoperative andthereby permit said holder to be moved further in thedirection of feed.

20. In an electric arc lamp having companion electrodes, a support forone of said electrodes, a holder for said electrode comprising a body towhich the electrode is secured, a hollow member securedto but insulatedfroml said body and adapted to be secured to said support, an electricalconductor in said hollow member connected to said body but insulatedfrom said member and adapted to carry current to said electrode, aholder for the other electrode, means for moving said holder and meansfor regulating the movement of said latter holder for maintaining asubstantially uniform are between said electrodes.

21. In an electrode feed mechanism, an electrode holder, means formoving said holder in the direction of feed, means for damping theaction of said means, means for engaging said holder within a range ofits movement, means for regulating the movement of said holder withinsaid range so as to maintain a substantially uniform arcand meansoperative upon said holder reaching the limit of said range to rendersaid engaging means inoperative and thereby permit said holder to bemoved further in the direction of feed, said damping means controllingsaid means first mentioned so that it moves said electrode holderrelatively-slowly in the direction of feed when said engaging means isinoperative.

22. In an electric arc lamp, an electrode holder comprising a body towhich an electrode is secured, a hollow stem connected to but insulatedfrom said Ebody and adapted to house the conjf

